1. Field of the Invention
The disclosed fabric is intended for use in the papermaking industry and finds application in the forming, wet press and dryer section of the papermaking equipment. The fabric is a carrying or conveying means used in the production of paper and is intended for use in applications requiring either a circular woven or a flat woven fabric. In the papermaking industry, fabrics of the instant invention, when used in the wet press or dryer section, are frequently referred to as felts since they generally comprise a carrier fabric, which runs in contact with the equipment, and a felt surface, which runs in contact with the paper. Likewise, fabrics used in the forming section are frequently referred to as Fourdrinier wires or simply wires and the forming section of the papermaking process is frequently referred to as the Fourdrinier section or equipment.
It has been recognized in the prior art that it is desirable to provide a felt for use in papermaking machinery comprising an under layer made of relative rigid non-deformable material having a compressible felt layer thereon. The under layer is generally expected to provide a desired void volume for receiving and carrying off water removed from the paper sheet. For example, as the fabric with the paper sheet thereon passes between the nip rollers in the press section, the felt is compressed and water is transferred from the paper sheet to the felt. The water is intended to migrate through the felt and to be voided through the voids provided in the under layer.
The prior art, has recognized that a felted surface used in combination with an under layer having a predetermined and controlled void volume may be utilized to provide a felt having relatively fine fibers for contacting the sheet of paper to be processed. U.S. Pat. Nos. 3,613,258; 4,199,753; 4,283,454 and 4,356,225 are representative of prior art attempts to control void volume.
In the forming section it has also been recognized that a high void volume or permeability in the base fabric is highly desirable. However, due to the nature of the papermaking process it is essential that the forming wire or fabric retain the fibrous material in the slurry while permitting rapid drainage of the fluid. One prior art attempt to produce a laminated non-woven papermakers Fourdrinier wire is disclosed in U.S. Pat. No. 3,121,660.
2. Summary of the Invention
The present invention provides a papermakers fabric having an under layer, comprised of a plurality of intermeshed preformed spirals, defining a void volume and an upper fabric layer adhered thereto. The upper fabric may be adhered to the under layer by the selective application of adhesive to the under layer and/or to the upper layer or may be achieved by including meltable adhesive means within the upper layer. The under layer and the upper layer are unified into a single fabric, such as by the application of heat and pressure efficient to activate the adhesive, and form a single fabric as used in the papermaking equipment.